In a field of medical treatment, one of the methods for sterilizing medical materials such as a surgical suit, a medical smock, medical appliances etc. includes a pressurized steam sterilization method in an autoclave. According to such sterilization method, the residual air in the autoclave causes a decrease in the effects on sterilization because of a potent adiabatic effect by the air. Especially, when the air is remained in the materials to be sterilized such as a surgical suit and a medical smock, even if heating by pressurized steam is performed, conduction of heat and humidity is disturbed leading a decrease in the effects on sterilization and sometimes poor sterilization. Therefore, in the pressurized steam sterilization method, the air in the materials to be sterilized that are placed in the autoclave is amply evacuated, and then the pressurized steam is provided in the autoclave to sterilize the materials.
After the air is evacuated from the autoclave by this means, to determine whether the autoclave operates normally for sufficient sterilization by the supplied pressurized steam therein, it is determined that the residual air that encumbers a flow of the pressurized steam supplied after the evacuation does not exist. One of such determination methods is Bowie and Dick Test which is termed as Bowie & Dick Test hereinafter. This Test contains following procedures. Packs sandwiching an indicator sheet that colors or discolors due to contacting with steam are inserted into the autoclave. By observing a coloring or discoloring state of the indicator sheet when pressurized steam sterilization is carried out by the prescribed procedures, it is determined that the residual air which encumbers a flow of the pressurized steam does not exist in the autoclave in order to determine whether the autoclave operates normally. In particular, this Test contains following specific procedures. Piled surgical towels are bundled to be in a certain size, the indicator sheet is disposed at the center thereof and then they are packed. After they are put into the autoclave, the autoclave is vacuumed and then the pressurized steam is introduced thereto. After heating is carried out at 134° C. for 3.5 minutes, the coloring or discoloring state of the indicator sheet is observed. If the indicator sheet is uniformly colored, it is determined that the residual air which encumbers the flow of the pressurized steam does not exist in the autoclave and thus the autoclave operates normally. On the other hand, if the indicator sheet is non-uniformly colored or discolored, it is determined that the residual air which encumbers the flow of the pressurized steam exists in the autoclave and thus the autoclave does not operate. Here, if the materials to be sterilized are put together therein, the materials are heat-sterilized again.
The appropriately plied and then bundled surgical towels as test equipment for Bowie & Dick Test having the indicator sheet at the center thereof are packed, and it is difficult to treat the packed towels due to bulkiness. Therefore, as simplified test equipment, for example, the Patent Document 1 discloses that a test pack having an indicator sheet disposed between porous bodies of piled plural non-woven fabrics entirely is covered by a paper cover sheet.